linux-kernel - Re: [PATCH 2/6] lightnvm: pblk: reduce arguments in __pblk_rb_update

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Message-Id: <5330486D-DD91-4980-B002-6BD9255835A4@lightnvm.io>
Date:   Mon, 2 Oct 2017 17:16:57 +0200
From:   Javier González <jg@...htnvm.io>
To:     Javier González <jg@...htnvm.io>
Cc:     Rakesh Pandit <rakesh@...era.com>,
        Matias Bjørling <mb@...htnvm.io>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] lightnvm: pblk: reduce arguments in
 __pblk_rb_update_l2p

> On 2 Oct 2017, at 13.32, Javier González <jg@...htnvm.io> wrote:
> 
>> On 1 Oct 2017, at 15.23, Rakesh Pandit <rakesh@...era.com> wrote:
>> 
>> We already pass the structure pointer so no need to pass the member.
>> 
>> Signed-off-by: Rakesh Pandit <rakesh@...era.com>
>> ---
>> drivers/lightnvm/pblk-rb.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>> 
>> diff --git a/drivers/lightnvm/pblk-rb.c b/drivers/lightnvm/pblk-rb.c
>> index 05e6b2e..920ffac 100644
>> --- a/drivers/lightnvm/pblk-rb.c
>> +++ b/drivers/lightnvm/pblk-rb.c
>> @@ -201,9 +201,9 @@ unsigned int pblk_rb_read_commit(struct pblk_rb *rb, unsigned int nr_entries)
>> 	return subm;
>> }
>> 
>> -static int __pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int *l2p_upd,
>> -				unsigned int to_update)
>> +static int __pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int to_update)
>> {
>> +	unsigned int l2p_update = rb->l2p_update;
>> 	struct pblk *pblk = container_of(rb, struct pblk, rwb);
>> 	struct pblk_line *line;
>> 	struct pblk_rb_entry *entry;
>> @@ -213,7 +213,7 @@ static int __pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int *l2p_upd,
>> 	int flags;
>> 
>> 	for (i = 0; i < to_update; i++) {
>> -		entry = &rb->entries[*l2p_upd];
>> +		entry = &rb->entries[l2p_update];
>> 		w_ctx = &entry->w_ctx;
>> 
>> 		flags = READ_ONCE(entry->w_ctx.flags);
>> @@ -230,7 +230,7 @@ static int __pblk_rb_update_l2p(struct pblk_rb *rb, unsigned int *l2p_upd,
>> 		line = &pblk->lines[pblk_tgt_ppa_to_line(w_ctx->ppa)];
>> 		kref_put(&line->ref, pblk_line_put);
>> 		clean_wctx(w_ctx);
>> -		*l2p_upd = (*l2p_upd + 1) & (rb->nr_entries - 1);
>> +		rb->l2p_update = (l2p_update + 1) & (rb->nr_entries - 1);

This is wrong. It should be rb->l2p_update when doing +1, otherwise you
are not using the updated l2p_update value. The result is the pipeline
stalling as the l2p pointer is left behind.

I'll fix it when picking it up.

Please test the patches before submitting.

Javier.

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